Heat pipe

About: Heat pipe is a research topic. Over the lifetime, 30354 publications have been published within this topic receiving 243669 citations. The topic is also known as: heatpipe & heat-pipe.

Thermal performance of a flat polymer heat pipe heat spreader under high acceleration

Abstract: This paper presents the fabrication and application of a micro-scale hybrid wicking structure in a flat polymer-based heat pipe heat spreader, which improves the heat transfer performance under high adverse acceleration. The hybrid wicking structure which enhances evaporation and condensation heat transfer under adverse acceleration consists of 100 µm high, 200 µm wide square electroplated copper micro-pillars with 31 µm wide grooves for liquid flow and a woven copper mesh with 51 µm diameter wires and 76 µm spacing. The interior vapor chamber of the heat pipe heat spreader was 30×30×1.0 mm3. The casing of the heat spreader is a 100 µm thick liquid crystal polymer which contains a two-dimensional array of copper-filled vias to reduce the overall thermal resistance. The device performance was assessed under 0–10 g acceleration with 20, 30 and 40 W power input on an evaporator area of 8×8 mm2. The effective thermal conductivity of the device was determined to range from 1653 W (m K)−1 at 0 g to 541 W (m K)−1 at 10 g using finite element analysis in conjunction with a copper reference sample. In all cases, the effective thermal conductivity remained higher than that of the copper reference sample. This work illustrates the possibility of fabricating flexible, polymer-based heat pipe heat spreaders compatible with standardized printed circuit board technologies that are capable of efficiently extracting heat at relatively high dynamic acceleration levels.

Cooling apparatus for a closed housing

Abstract: A cooling apparatus for a housing which is provided with an opening at the upper part thereof, comprises a casing located on the upper part of the housing and including a bottom plate to close the opening and a chamber, a partition wall provided in the casing to divide the chamber into a first chamber section and a second chamber section, heat exchanger including at least one heat pipe provided in the casing through the partition wall with coolant therein for exchanging heat in the first chamber section with heat in the second chamber section. The heat pipe has one end portion in the first chamber section and the other end portion in the second chamber section, and inclines with the one end portion located lower than the other end portion.

Temperature Response of Heat Transport in a Micro Heat Pipe

Abstract: A detailed mathematical model for predicting the heat transport capability and temperature gradients that contribute to the overall axial temperature drop as a function of heat transfer in a micro heat pipe has been developed. The model utilizes a third-order ordinary differential equation, which governs the fluid flow and heat transfer in the evaporating thin film region; an analytical solution for the two-dimension heat conduction equation, which governs the macro evaporating film region in the triangular corners; the effects of the vapor flow on the liquid flow in the micro heat pipe; the flow and condensation of the thin film caused by the surface tension in the condenser; and the capillary flow along the axial direction of the micro heat pipe. With this model, the temperature distribution along the axial direction of the heat pipe and the effect on the heat transfer can be predicted. In order to verify the model presented here, an experimental investigation was also conducted and a comparison with experimental data made

Condensation, evaporation and boiling of falling films in wickless heat pipes (two-phase closed thermosyphons): A critical review of correlations

Abstract: With the objective of estimating the thermal resistance of a two-phase closed thermosyphon (TPCT), the work presented is a state of the art of condensation and falling film evaporation/boiling correlations. A deep analysis of up-to-date reported equations dealing with falling film heat transfer is carried out and recommendations are provided to select the most suitable and reliable correlations. Mechanisms such as filmwise condensation and Nusselt theory, falling film development in the thermal entry length (TEL), film thickness, appearance of waves and turbulence, two-phase flow interaction and entrainment with the shear stress at the liquid-vapour interface, falling film evaporation and boiling, in addition to film breakdown, are comprehensively explained and discussed. For all sections, the advised correlations are reported in a clear and simple way using tables. The objective of this paper is to cover sufficient knowledge on the falling film dynamic in thermosyphons to ease the prediction of heat transfer coefficients. This paper can be taken as a starting point for thermosyphon users in the study of falling film heat transfer in wickless heat pipes.

Loop Heat Pipes: A Review of Fundamentals, Operation,and Design

Abstract: The loop heat pipe (LHP) is a passive two-phase heat transport device that is gaining importance as a part of spacecraft thermal control systems and also in applications such as in avionics cooling and submarines. A major advantage of a loop heat pipe is that the porous wick structure is confuned to the evaporator section, and connection between the evaporator and condenser sections is by smooth tubes, thus minimizing pressure drop. A brief overview of loop heat pipes with respect to basic fundamentals, construction details, operating principles, and typical operating characteristics is presented in this paper. Finally, the paper presents the current developments in modeling of thermohydraulics and design methodologies of LHPs.